Instead of a latched door, I decided to use a theft resistant lock bolt instead. There are many theft resistant/proof lock bolts and nuts available in the automotive market. However rugged, they are generally bulky and heavy. A good example is the theft resistant wheel locks (picture left). The head of the bolt has a unique design (according to their ad) such that there can only be one key shape to turn the wheel lock.  I bought a lock set from McGuard and it came with 4 lock lugs and a special key. Picture left is one of the 4 lock lugs with a special head design. You need an opposing key (of exact mirror image) to turn the lock lug.

The idea is to integrate this lock lug set into my opening/closing canopy latch system - such that I can eliminate the need for a door, door lock and seal etc. My canopy latch system is shown at the left (also in the following Section 19). The canopy can be latched/unlatched by pushing or pulling the handle (counterclockwise or clockwise) respectively. The center of rotation of the handle is shown (red arrow left). By connecting the center of rotation of the handle to the lock lug, I can latch/unlatch the canopy from the outside using the 'special key' for the lock lugs.

Lock Construction

I took the 'special key' and turned it down to a minimum diameter of the lock design and pressed it into the center of rotation of the handle (lower part). The second part of the locking mechanism consists of a brass tube that is pressed into an aluminum holder with 2 slotted holes. The 'key handle' can be slipped into the brass tube, snug fit, but with free rotation. To keep the 'key handle' from sliding out of the brass tube, a groove is carved into the body of the 'key handle'. A tapped hole with a hex screw is added to the top of the holder. The hex screw, penetrating through the brass tubing and into the groove, prevents the 'key handle' from sliding out.

I drilled two counter-sink holes through the longerons for mounting the lock holder in place. The outboard end of the brass tube protrudes through the fuselage (picture below). As I turn the lock handle counter-clockwise, it pulls the canopy lock to the closed position. 

The key, in my case is the wheel nut itself. One benefit for the reverse role is that I have 4 wheel nuts available as the key. If I lose one, I'll have three more to go. I can also hide one in the plane somewhere if necessary. I have yet to shave the brass tubing flush to the fuselage and add a plug to seal the tubing while parked or in flight.

This locking approach works well, it does not take much of an effort to open or lock the canopy. I have eliminated the door and door lock as well.